I assume that someone who knows what they are talking about will be along shortly. However, as a guess, could it be the password in (Win 7) in control panel, network and sharing centre, choose home group and sharing options, view or print the homegroup password. ?? As none of the other pcs at home have ever needed this, (they are either pre-7, or we do not fully share stuff - eg visitors posh laptops), I've often wondered what it is for!!